Voltage converter

ABSTRACT

A voltage converter delivers an output voltage between a first and a second node. The voltage converter includes a capacitor series-coupled with a resistor between the first and second nodes. The resistor is coupled in parallel with a bidirectional switch receiving at its control terminal a positive bias voltage referenced to the second node.

PRIORITY CLAIM

This application claims the priority benefit of French Application forPatent No. 2012211, filed on Nov. 26, 2020, the content of which ishereby incorporated by reference in its entirety to the maximum extentallowable by law.

TECHNICAL FIELD

The present disclosure relates generally to electronic devices, and,more specifically, to AC/DC converters. The present disclosure generallyapplies to any circuit using a rectifying bridge as an AC/DC converter.

BACKGROUND

Many AC/DC converter architectures, based on controllable rectifyingelements, for example, thyristors (or SCRs, for Silicon ControlledRectifiers), or non-controllable rectifying elements, such as diodesassembled as a rectifying bridge, powered with an AC voltage anddelivering a DC voltage, are known.

The inrush current, that is, the current peaks which occur on eachhalfwave of the AC voltage as long as the voltage across a capacitor atthe output of the rectifying bridge has not reached a sufficient level,particularly in starting phases, is generally desired to be limited.

There is a need in the art to overcome all or part of the disadvantagesof known voltage converters.

SUMMARY

One embodiment provides a voltage converter delivering an output voltagebetween a first node and a second node, the voltage converter being orincluding a capacitor series-coupled with a resistor between the firstand second nodes, the resistor being coupled in parallel to abidirectional switch receiving at its control terminal a positive biasvoltage referenced to the second node.

According to an embodiment, the converter may include a voltagerectifying bridge.

According to an embodiment, a control current is injected into thecontrol terminal and, for a first value of the control current, theswitch blocks flow of a positive current from the first node to thesecond node. For a second value of the control current, the switchallows flow of a positive current from the first node to the secondnode.

According to an embodiment, the flow of a negative current from thesecond node to the first node is independent from the control current.

According to an embodiment, the switch may be or include a diode havingits cathode coupled to the first node and having its anode coupled tothe second node.

According to an embodiment, the switch may be or include a thyristorhaving its cathode coupled to the second node and having its anodecoupled to the first node, the thyristor receiving the bias voltage onits gate, the control current being injected into the gate.

According to an embodiment, the switch may be or include a transientvoltage suppressor circuit coupled between the anode of the thyristorand the gate of the thyristor.

According to an embodiment, the switch may be or include a first triac,the first anode of the first triac being coupled to the first node andthe second anode of the first triac being coupled to the second node.

According to an embodiment, the switch may be or include a second triaccoupled between the gate of the first triac and the second node, thesecond triac being controlled by the control current.

According to an embodiment, a first anode of the second triac is coupledto the second node and a second anode of the second triac is coupled tothe gate of the first triac.

According to an embodiment, the switch may be or include a transientvoltage suppressor circuit coupled between the gate of the first triacand the second node.

According to an embodiment, the transient voltage suppressor circuit maybe a transil diode.

Also disclosed herein is a voltage converter including: a rectifyingbridge having first and second outputs directly electrically connectedto first and second nodes, wherein an input voltage is received betweenfirst and second inputs of the rectifying bridge; a capacitance directlyelectrically connected between the first node and a third node; aresistance directly electrically connected between the third node andthe second node; and a bidirectional switch directly electricallyconnected between the third node and the second node, the bidirectionalswitch having a control terminal, wherein the control terminal receivesa control signal.

The bidirectional switch may include: a first triac having a first anodedirectly electrically connected to the third node and a second anodedirectly electrically connected to the second node, the first triacfurther having a gate directly electrically connected to a fourth node;and a second triac having a first anode directly electrically connectedto the gate of the first triac, a second anode directly electricallyconnected to the second node, the second triac having a gate receivingthe control signal.

A transient voltage suppressor circuit may be directly electricallyconnected between the fourth node and the second node.

The transient voltage suppressor circuit may be a transil diode.

The bidirectional switch may include: a diode having a cathode directlyelectrically connected to the third node and an anode directlyelectrically connected to the second node; and a thyristor having ananode directly electrically connected to the third node, a cathodedirectly electrically connected to the second node, and a gate directlyelectrically connected to a fourth node, wherein the gate receives thecontrol signal.

A transient voltage suppressor circuit may be directly electricallyconnected between the third node and the fourth node.

The transient voltage suppressor circuit may be a transil diode.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing features and advantages, as well as others, will bedescribed in detail in the following description of specific embodimentsgiven by way of illustration and not limitation with reference to theaccompanying drawings, in which:

FIG. 1 schematically shows an embodiment of a voltage converterdisclosed herein;

FIG. 2 shows in further detail an embodiment of a voltage converterdisclosed herein; and

FIG. 3 shows in further detail another embodiment of a voltage converterdisclosed herein.

DETAILED DESCRIPTION

Like features have been designated by like references in the variousfigures. In particular, the structural and/or functional features thatare common among the various embodiments may have the same referencesand may dispose identical structural, dimensional and materialproperties.

For the sake of clarity, the steps and elements that are useful for anunderstanding of the embodiments described herein have been illustratedand described in detail. In particular, the various possibleapplications of the embodiments of voltage converters are not detailed.

Unless indicated otherwise, when reference is made to two elementsconnected together, this signifies a direct connection without anyintermediate elements other than conductors, and when reference is madeto two elements coupled together, this signifies that these two elementscan be connected or they can be coupled via one or more other elements.

In the following disclosure, unless otherwise specified, when referenceis made to absolute positional qualifiers, such as the terms “front”,“back”, “top”, “bottom”, “left”, “right”, etc., or to relativepositional qualifiers, such as the terms “above”, “below”, “higher”,“lower”, etc., or to qualifiers of orientation, such as “horizontal”,“vertical”, etc., reference is made to the orientation shown in thefigures.

Unless specified otherwise, the expressions “around”, “approximately”,“substantially” and “in the order of” signify within 10%, and preferablywithin 5%.

FIG. 1 schematically shows an embodiment of a voltage converter 10.

Voltage converter 10 receives, as an input, a voltage Vin. In otherwords, converter 10 comprises two input nodes 12 and 14, with voltageVin being delivered between nodes 12 and 14. Input nodes 12 and 14 are,for example, coupled across an AC voltage source (not shown) which maybe, for example, an electric power distribution system.

Converter 10 outputs an output voltage Vout. Voltage Vout is, forexample, a DC voltage. Voltage Vout is delivered between two nodes 16and 18. Node 18 corresponds to a reference potential, for example,ground. Voltage Vout is referenced to the reference potential on node18.

Converter 10 comprises a circuit 20 receiving voltage Vin and deliveringvoltage Vout. Circuit 20 is coupled, preferably connected, to inputnodes 12 and 14 and to output nodes 16 and 18. Circuit 20 comprises arectifying bridge, details of which are not shown in FIG. 1.

Converter 10 comprises a capacitor 22 and a resistor (R) 24series-coupled between output nodes 16 and 18. More particularly, one ofthe terminals of capacitor 22 is coupled, preferably connected, to node16. A second terminal of the capacitor is coupled, preferably connected,to a node 26. A terminal of resistor 24 is coupled, preferablyconnected, to node 26. The other terminal of resistor 24 is coupled,preferably connected, to node 18.

Converter 10 further comprises a circuit 28. A terminal of circuit 28 iscoupled, preferably connected, to node 26. Another terminal of circuit28 is coupled, preferably connected, to node 18. Circuit 28 comprises acontrol input or terminal. The control input receives a control signalComm, more particularly a positive bias voltage referenced to thevoltage on node 18, in other words, referenced to the same voltage asthe output voltage (that is, for example, referenced to ground), and acontrol current.

Circuit 28 corresponds to a bidirectional switch. In other words, acurrent may flow through circuit 28 in one direction or in the oppositedirection. In other words, a positive current may flow from node 26 tonode 18 and a negative current can flow from node 18 to node 26. Atleast one of the directions, namely the direction from node 26 to node18 corresponding to a positive current, may be controlled by controlsignal Comm. Thus, preferably, circuit 28 conducts a positive currentfrom node 26 to node 18 for one or a plurality of first values of thecontrol current and blocks (that is, prevents the flowing of) a negativecurrent for one or a plurality of second values of the control current.

According to an embodiment, the negative current flows whatever is avalue of control signal Comm.

According to another embodiment, the negative current is conducted bycircuit 28 for a signal Comm having a value among the first value(s),and is blocked by circuit 28 for a signal Comm having a value among thesecond value(s). In other words, the first value(s) enable the currentto flow in both directions, and the second value(s) block the flowing ofthe current in both directions.

At the starting of operation of the converter, a current peak generallyappears in the current flowing through capacitor 22. Such a current peakmight cause damage to the components. To limit such a current peak, itis desired to run the current through resistor 24 to attenuate the peakwithout attenuating the current outside of the peak. Thus, circuit 28blocks the flowing of the positive current from node 26 to node 18through the branch comprising circuit 28, and ensures that the currentflows through resistor 24. In other words, during the period likely tocomprise a current peak, that is, at the starting of the converter, thecontrol current has a value such that a positive current is blockedbetween the input and the output of circuit 28 and such that saidpositive current flows through the resistor.

When such a current peak appears at the starting of the converter, thecurrent flows from node 16 to node 18. It is thus generally not uselessto block the negative current flowing through circuit 28.

FIG. 2 shows in further detail an embodiment of a voltage converter 50.Converter 50 is an embodiment of the converter 10 of FIG. 1. Thus,converter 50 comprises capacitor 22, circuit 28, and circuit 20, coupledas described in relation with FIG. 1.

Circuit 20 comprises a rectifying bridge. In the example of FIG. 2, therectifying bridge is a diode rectifying bridge. The rectifying bridgethus comprises four diodes 52, 54, 56, and 58.

Diodes 52 and 56 are series-coupled between node 16 and node 18, thatis, between the output nodes, that is, between the nodes of applicationof output voltage Vout. More particularly, diode 52 is coupled betweennode 16 and a node 60 and diode 56 is coupled between node 60 and node18. In other words, the cathode of diode 52 is coupled, preferablyconnected, to node 16 and the anode of diode 52 is coupled, preferablyconnected, to node 60. Further, the cathode of diode 56 is coupled,preferably connected, to node 60 and the anode of diode 56 is coupled,preferably connected, to node 18.

Diodes 54 and 58 are series-coupled between node 16 and node 18, thatis, between the output nodes, that is, between the nodes of applicationof output voltage Vout. More particularly, diode 54 is coupled betweennode 16 and a node 62, and diode 58 is coupled between node 62 and node18. In other words, the cathode of diode 54 is coupled, preferablyconnected, to node 16 and the anode of diode 54 is coupled, preferablyconnected, to node 62. Further, the cathode of diode 58 is coupled,preferably connected, to node 62 and the anode of diode 58 is coupled,preferably connected, to node 18.

Thus, the rectifying bridge comprises two branches coupled in parallel,each branch comprising two diodes coupled in series, diodes 52 and 56 ordiodes 54 and 58. The diodes of a same branch are series-coupled so thatthe cathode of one of the two diodes is coupled, preferably connected,to the anode of the other diode.

As a variant, at least some of diodes 52, 54, 56, and 58 may be replacedwith another electronic component enabling forming of a rectifyingbridge. For example, at least one of diodes 52, 54, 56, and 58, forexample, two of diodes 52, 54, 56, and 58, may be replaced withcontrollable elements, for example, thyristors or transistors.

Circuit 20, for example, comprises inductances 64 and 66. Inductance 64is, for example, coupled between node 60 and input node 12. Inductance66 is, for example, coupled between node 62 and input node 14. Moreparticularly, a terminal of inductance 64 is coupled, preferablyconnected, to node 60 and the other terminal of inductance 64 iscoupled, preferably connected, to node 12. Similarly, a terminal ofinductance 66 is coupled, preferably connected, to node 62 and the otherterminal of inductance 66 is coupled, preferably connected, to node 14.

Circuit 28 comprises a diode 68. Diode 68 is coupled between node 26 andnode 18. Diode 68 is coupled in reverse. In other words, diode 68 iscoupled to allow the flowing of a negative current from node 18 to node26. In other words, the cathode of diode 68 is coupled, preferablyconnected, to node 26. The anode of diode 68 is coupled, preferablyconnected, to node 18. Diode 68 is thus coupled in parallel to resistor24.

Circuit 28 comprises a thyristor 70. Thyristor 70 is coupled betweennode 26 and node 18. Thyristor 70 is coupled to allow the flowing of apositive current from node 26 to node 18. In other words, the cathode ofthyristor 70 is coupled, preferably connected, to node 18. The anode ofthyristor 70 is coupled, preferably connected, to node 26. Thyristor 70is thus coupled in parallel to resistor 24. Thyristor 70 is thus coupledin parallel and head-to-tail with diode 68.

Thyristor 70 is, for example, a cathode-gate thyristor. The thyristorreceives on its gate a voltage referenced to node 18. The thyristor gatereceives the bias voltage of control signal Comm. The thyristor's gateis thus biased by a positive voltage referenced to node 18. A controlcurrent is injected into the gate to determine the on or off state ofthe thyristor.

At the starting of the converter, a positive current flows from node 26to node 18. The control current has, at the starting, a value enablingto turn on thyristor 70. Further, diode 68 is non-conductive of thecurrent flowing from node 26 to node 18. The current thus flows throughresistor 24, which enables attenuation of the current peak appearing atthe starting.

After the starting, that is, after the current peak generated at thestarting, the control current takes a value turning on thyristor 70.Thus, during the operation, that is, during the steady state of theconverter, the current at least partially, preferably mostly, flowsthrough diode 68 or thyristor 70, according to the direction of thecurrent.

Preferably, circuit 28 comprises a transient voltage suppressor, TSV,circuit 72. Circuit 72 enables avoiding damage that might be caused tothe converter by a transient voltage or overvoltage when the system isoff, in other words when the capacitor 22 is discharged and thethyristor 70 is blocked, meaning that the thyristor 70 is not receivinga control signal corresponding to an on state. For example, during anovervoltage caused by lightning, a strong current flows through thecapacitor 22 and through the resistor 24. Under the effect of thiscurrent, the voltage across the terminals of the resistor 24 increasesand reaches the threshold voltage of circuit 72. Once this thresholdvoltage reached, a current flows from node 23 to node 18, throughcircuit 72, by the triggering of the thyristor 70 and causing of thechange of the thyristor to an on state. The thyristor 70, by becomingon, short-circuits the resistor 24 and stops the voltage to reach acritical value for the converter. For example, circuit 72 is a transildiode, for example a unidirectional transil diode. Preferably, circuit72 is coupled between node 26 and the gate of thyristor 70. A terminalof circuit 72 is for example coupled, preferably connected, to node 26and another terminal of circuit 72 is for example coupled, preferablyconnected, to node 18.

Preferably, circuit 72 is configured to form a short-circuit between thegate of thyristor 70 and node 26 if the voltage across thyristor 70 is,for example, greater than 50 V, preferably greater than 100 V,preferably greater than 200 V. Thus, when the voltage across thyristor70 is greater than the selected threshold, the thyristor receives at itsgate the voltage at node 26 and turns on, allowing the dissipation ofthe current peak in the thyristor, while limiting the voltage to which acircuit powered by the voltage Vout is subjected.

FIG. 3 shows in further detail an embodiment of a voltage converter 80.Converter 80 is an embodiment of the converter 10 of FIG. 1. Thus,converter 80 comprises capacitor 22, circuit 28, and circuit 20, coupledas described in relation with FIG. 1. Circuit 20 comprises, in theexample of FIG. 3, the same elements as the circuit 20 described inrelation with FIG. 2, coupled in the same way. The circuit 20 of FIG. 3is thus identical to the circuit 20 of FIG. 2.

Converter 80 of FIG. 3 differs from the converter 50 of FIG. 2 by thecomposition of circuit 28. The circuit 28 of FIG. 3 comprises a triac 82coupled between node 26 and node 18. In other words, a terminal of triac82, preferably the first anode, that is, the anode on the gate side, iscoupled, preferably connected, to node 26 and another terminal of triac82, for example, the second anode, is coupled, preferably connected, tonode 18.

Preferably, triac 82 is capable of operating in the first and thirdquadrants Q1 and Q3. First quadrant Q1 indicates an operating statewhere the current flows from node 18 to node 26, the voltage on node 18is greater than the voltage on node 26, and the current in the gate oftriac 82 flows towards triac 82. Third quadrant Q3 indicates anoperating state where the current flows from node 26 to node 18, thevoltage on node 26 is greater than the voltage on node 18, and thecurrent in the gate of triac 82 flows from triac 82.

Triac 82 is preferably capable of withstanding high currents, forexample, powers in the range from 500 W to 10 kW under a voltage of 230V.

Circuit 28 further comprises a triac 84 coupled between the gate oftriac 82 and node 18. In other words, a terminal of triac 84,preferably, the first anode, is coupled, preferably connected, to node18 and another terminal of triac 84, for example, the second anode, iscoupled, preferably connected, to the gate of triac 82. Triac 84receives the control current Comm on its gate to control triac 84.Further, the gate of triac 84 is biased by the bias voltage. Thus, thegate of triac 84 is biased to a positive voltage referenced to node 18.

Preferably, triac 84 is capable of operating in the first and fourthquadrants Q1 and Q4. Fourth quadrant Q4 indicates an operating statewhere the current flows from node 26 to node 18, the voltage on node 26is greater than the voltage on node 18, and the current in the gate oftriac 84 flows towards triac 84.

At the starting of the converter, a positive current flows from node 26to node 18. The control current has, at the starting, a value, forexample a null value, enabling to turn off triac 84. Triac 82 is thusoff. The current thus flows through resistor 24, which enables todecrease the current peak appearing at the starting.

After the starting, that is, after the current peak generated at thestarting, the control current takes a value turning on triac 84, andthus turning on triac 82. Thus, during the operation, that is, duringthe steady state of the converter, the current at least partially flows,preferably mostly, through triac 82.

Preferably, circuit 28 comprises a transient voltage suppressor, TSV,circuit 86. Circuit 86 enables avoiding damage that could be caused tothe converter by an overcurrent when the system is off, for example, anover current caused by lightning. For example, circuit 86 is a transildiode. Preferably, circuit 86 is coupled between node 18 and the gate oftriac 82. A terminal of circuit 86 is for example coupled, preferablyconnected, to node 18 and another terminal of circuit 86 is for examplecoupled, preferably connected, to the gate of triac 82.

Preferably, circuit 86 is configured to form a short-circuit between thegate of triac 82 and node 18 if the voltage across triac 82 is forexample greater than 50 V, preferably greater than 100 V, preferablygreater than 200 V. Thus, when the voltage across triac 82 is greaterthan the selected threshold, triac 82 receives on its gate the voltageon node 18 and turns on, allowing the dissipation of the current peak intriac 82.

An advantage of the described embodiments is that they enableattenuation of current peaks in capacitor 22 at the starting of theconverter.

An advantage of the described embodiments is that they enable use of acontrol signal of circuit 28 referenced to the same node as the othervoltage already present in the circuit, for example, at the same node asvoltage Vout. It is thus not necessary to supply a different auxiliarypower and it is possible to use a voltage already present in the device.

Various embodiments and variants have been described. Those skilled inthe art will understand that certain features of these variousembodiments and variants may be combined, and other variants will occurto those skilled in the art.

Finally, the practical implementation of the described embodiments andvariations is within the abilities of those skilled in the art based onthe functional indications given hereabove.

1. A voltage converter delivering an output voltage between a first anda second node, comprising: a capacitor series-coupled with a resistorbetween the first and second nodes; and a bidirectional switch coupledin parallel with the resistor, wherein the bidirectional switch isconfigured to receive at its control terminal a positive bias voltagereferenced to the second node; wherein the bidirectional switchcomprises: a first triac having a first anode coupled to the first nodeand a second anode coupled to the second node; and a second triac havingcoupled between a gate of the first triac and the second node, thesecond triac being controlled by the positive bias voltage.
 2. Thevoltage converter according to claim 1, further comprising a voltagerectifying bridge coupled between the first and second nodes.
 3. Thevoltage converter according to claim 1, wherein a control current isinjected into the control terminal of the bidirectional switch, and thebidirectional switch blocks flowing of a positive current from the firstnode to the second node if the control current has a first value, andthe bidirectional switch allows the flowing of the positive current fromthe first node to the second node if the control current has a secondvalue different than the first value.
 4. The voltage converter accordingto claim 3, wherein a negative current flowing from the second node tothe first node is independent from the control current.
 5. The voltageconverter according to claim 1, wherein a first anode of the secondtriac is coupled to the second node and a second anode of the secondtriac is coupled to the gate of the first triac.
 6. The voltageconverter according to claim 1, wherein the bidirectional switchcomprises a transient voltage suppressor circuit coupled between thegate of the first triac and the second node.
 7. The voltage converteraccording to claim 6, wherein the transient voltage suppressor circuitcomprises a transil diode.
 8. A voltage converter comprising: arectifying bridge having first and second outputs directly electricallyconnected to first and second nodes, wherein an input voltage isreceived between first and second inputs of the rectifying bridge; acapacitance directly electrically connected between the first node and athird node; a resistance directly electrically connected between thethird node and the second node; and a bidirectional switch directlyelectrically connected between the third node and the second node, thebidirectional switch having a control terminal, wherein the controlterminal receives a control signal.
 9. The voltage converter of claim 8,wherein the bidirectional switch comprises: a first triac having a firstanode directly electrically connected to the third node and a secondanode directly electrically connected to the second node, the firsttriac further having a gate directly electrically connected to a fourthnode; and a second triac having a first anode directly electricallyconnected to the gate of the first triac, a second anode directlyelectrically connected to the second node, the second triac having agate receiving the control signal.
 10. The voltage converter of claim 9,further comprising a transient voltage suppressor circuit directlyelectrically connected between the fourth node and the second node. 11.The voltage converter of claim 10, wherein the transient voltagesuppressor circuit comprises a transil diode.
 12. The voltage converterof claim 8, wherein the bidirectional switch comprises: a diode having acathode directly electrically connected to the third node and an anodedirectly electrically connected to the second node; and a thyristorhaving an anode directly electrically connected to the third node, acathode directly electrically connected to the second node, and a gatedirectly electrically connected to a fourth node, wherein the gatereceives the control signal.
 13. The voltage converter of claim 12,further comprising a transient voltage suppressor circuit directlyelectrically connected between the third node and the fourth node. 14.The voltage converter of claim 13, wherein the transient voltagesuppressor circuit comprises a transil diode.